The intertidal rocky shore

identifying brown seaweeds of the intertidal rocky shore

The brown seaweeds are tough and able to live
in wave-exposed waters near the surface. They are the most common seaweeds
of the intertidal rocky shore, usually found in and below the sublitoral
fringe.

brown seaweedsAll the big and strong seaweeds in New Zealand, and perhaps
in the world, consist of brown seaweeds. They are able to live close to
the surface, in bright light with a high dose of ultraviolet.The stringy bladderweeds are tough, flexible and streamlined,
and they can survive strong to extreme wave action.

f210515: the bull kelp (Durvillea antarctica) has
a single round stipe sprouting from a large round holdfast. The fronds
branch out to whip-like leaves that float on the water. Inside these leaves
the plant has a honey-comb structure. In sheltered waters, the leaves are
not whip-like but more flat and also floating.

f210223: bull kelp (Durvillea antarctica) in wild
water makes whip-like fronds that yield to the water movement while floating
on the surface. This is a good strategy to minimise wave stress. These
leaves can grow to 10m in length. The hollow leaves have been used by early
Maori to store and preserve muttonbird (a shearwater).

the giant bladderkelp (Macrocystis pyrifera) has narrow
but extremely tough stems from which branch float bladders with a long
narrow leaf attached. Its holdfast can grow multiple stems, which can grow
to 30m long, depending on the light conditions at the bottom. Swimming
through a forest of these 15-20m tall, strictly parallel 'trees' is an
awesome experience. Unfortunately, because seas are becoming murkier, the
giant kelp can no longer establish itself in deep water. In shallow water
it can grow only where the pebbly bottom it prefers, is not stirred, and
there must also be enough light for its spores to develop.

f027104: the giant kelp (Macrocystis pyrifera) in shallow
water, beginning to tower over all other seaweeds.

f980326: bullkelp is washed up on the beach because it floats.
Here it dries up to tough hard masses that decompose only very slowly.
Ancient Maori used the bullkelp as a bag for storing food in.

f026724: below the floating bullkelp Durvillea antarctica
grows a young branched Durvillea Willana on a very strongly attached
holdfast. From the intertidal, looking down into the sea, one can hardly
imagine how massive this seaweed becomes.

f026435: a diver visits a forest of branching bullkelp (Durvillea
willana) whose leaves can grow to a colossal size, one metre wide by
five metres long and very thick as well. When these flap around, one must
be careful not to get hit.

f051711: the necklace weed (Hormosira banksii) or
Neptune's necklace can store much water in its bladders, which protects
it against drying out. It prefers calm conditions and is usually found
inside harbours and on the fringe of rockpools. In sheltered waters its
beads
are large; in exposed sites small.

f034931: the wiry weed (Carpophyllum angustifolium)
has a thin but very strong stem and small leaves. It survives in the wildest
of waters, near the surface of highly exposed reefs where no other seaweeds
can grow. Its thin stems are so strong that a man has great problems breaking
them. Divers sometimes call it Number Eight wire.

f051700: the broccoli weed or cartilageous weed (Xiphophora
chondrophylla) has flat stems that branch in a flat plane but at the
extremities it forms a broccoli-like head. The thick stems are strong and
store much water, which allows it to grow at the low tide in moderate exposure.

f051703: a broccoli weed (Xiphophora chondrophylla)
begins life by spreading itself in a horizontal plane. The broccoli weed
feels a bit like cartilage (Greek: chondros).

f051111: the flapjack (Carpophyllum maschalocarpum)
has flat stems that branch in a flat plane with pointed leaves and large
pointed float bladders. Its strength rates in between the strong wiry weed
and the featherweed. It tolerates short exposure to sun and air and prefers
to live in sheltered to moderately exposed conditions.

f050217: the feather weed (Carpophyllum flexuosum)
is not very strong and prefers to live in moderate exposure where it is
not prone to drying out. It has a flat stem and finely branched leaves
and small float bladders. It is believed that it has several growth forms,
but these may well be separate species. found on E side of N Island.

Xiphophora gladiata, the slender cartilage weed grows
much like X. chondrophylla at low tide level, and is tough. Its branches
are thick and flat and with y-shaped ends.

Sargassum sinclairii, the sargasso weed has a fine
structure with undulating leaves and small float bladders. It is pretty.

Marginariella boryana has long strap-like blades splitting
from a domed holdast consisting of fibrous branchlets. Reproductive fronds
have long yellow or brown vesicles hanging off in a row. Mainly from Wellington
south.

Undaria pinnafitida is an invasive species from Japan
where it is called Wakame. It is pen shaped with a large midrib and slimy
blade. A frilled sporophyll is found at the base of adult plants. Manily
from Wellington south.

Petalonia fascia (15cm) a cluster of small slimy light
brown blades originating from a crust base.

Scytosiphon lomentaria (10-30cm) a brown slim seaweed
forming sausage-like chains. Sausages can be tubular or flattened. Seasonal
in winter-spring in upper intertidal. slippery. Mainly on the South Island.

Adenocystis utricularis (2-9cm) a brown seaweed with
water-filled bladders, firm and swollen, originating from a small round
holdfast. Found on open coasts in the lower mid-tidal.

f006828: the stalked kelp (Ecklonia radiata) stands
erect by the stiffness of its stalk, rather than by float bladders. Its
large crown makes it susceptible to being pulled off the rocks by waves,
so it prefers the calm of the deep. Here a sea urchin is considering to
clear-fell it, as it is standing inside the urchin barren zone.

f048401: the flexible weed (Carpophyllum flexuosum)
has an almost straight flat stem and long leaves with a mid-rib and smooth
edges. It is not strong and prefers calm conditions. The flexible weed
is particularly successful inside harbours, as it is able to shed deposition
by sloughing it off.

f048306: in sheltered conditions the flexible weed (Carpophyllum
flexuosum) can grow over 6 m tall, at times forming veritable forests,
but such forests can disappear overnight by a large storm.

f042030: the zigzag sausage weed (Cystophora torulosa)
has a round stem that zig-zags in between each side branch. Its leaves
look like sausages. It has small float bladders.

f032335: the pillow weed (Colpomenia sinuosa) is hollow
inside but not able to retain water. It is found in stable rock pools and
can grow on other seaweeds.

slender zigzag weed (Cystophora retroflexa) looks
a bit like featherweed but has a zigzag stipe. East coast North Island.